The present invention relates to a method and apparatus for using a narrowband, multichromatic electromagnetic radiation emitter to photomodulating living tissue and, in particular, human cell-containing tissue. By exposing living tissue to electromagnetic radiation in carefully chosen wavelength-bands of the spectrum either continuously for a period of time or in pulses of a predetermined frequency, cells within living tissue can be stimulated to begin genetically determined routines or regenerative functions or inhibited from these same functions. The novel photomodulation apparatus and method can be used to control, stimulate, or inhibit cell growth to treat conditions caused by undesirable or suboptimal cell growth or cell function.
It is traditionally accepted that the coherent nature of laser light (which is one of the properties that sets laser light apart form all other light) is necessary for the current applications of light sources used in medical treatment. This is particularly true for biostimulatory or bioinhibitory effects in living tissue since essentially all of the research is with lasers. Lasers, however, are very expensive devices, require large amounts of power, and can be extremely dangerous unless used under the strict supervision of qualified medical personnel. Further, lasers have long been believed to be essentially the only suitable source of electromagnetic radiation for generating effective biostimulatory or bioinhibitory effects because it was assumed that the light source must be monochromatic, that is of a single pure color or wavelength, i.e., is monchromaticxe2x80x94operating in a narrow spectrum of wavelengths. While other narrowband, multichromatic emissions sources have been known, such as laser diodes and, more generally, light emitting diodes (xe2x80x9cLEDsxe2x80x9dxe2x80x94devices capable of emitting electromagnetic radiation in a narrow spectrum of wavelengths), LEDs have never been widely accepted as suitable for use in medical treatment due to their limited power output and the low intensity of electromagnetic radiation they are capable of delivering to the living tissue receiving treatment. Moreover, despite the recent emergence of very high brightness LEDs, interest in the use of LEDs as a replacement for lasers in applications such as dermatological treatment, for example, has not become known within the art.
The lack of interest in using LEDs to replace lasers for medical treatment may be because most current lasers have very short pulse duration and also very high peak power. These are both properties that cannot be achieved by current LEDs and might never be. However, new lasers for treating unwanted hair and veins have more recently been developed that are xe2x80x98long pulsedxe2x80x99 and also use much lower peak power. As well, most biostimulatory experiments have used higher energies than those possible with LEDs. The thought of stringing hundreds or thousands of LEDs together has never been considered as it may have been considered to be an optical challenge for some applications.
Most laser technology applied for medical use is adapted from military laser technology and only more recently has the development of laser systems specifically created for medical use become commonplace, so LED systems that could be adapted for living tissue were not pre-existing like the lasers. Almost all laser research is directed at delivering the laser beam through mirror or fiber optics to living tissue. The maximum beam diameter is determined usually by the diameter of the lasing medium laser head. While it is commonplace to xe2x80x98narrowxe2x80x99 the beam diameter from that exiting the laser head, making the beam wider is rarely done as preserving the desired-required treatment parameters laser qualities becomes a significant optical issue and there is insufficient power to cover large areas with these parameters. Simply put, no one has been thinking of trying to cover say a square foot of surface with a laser beam, and currently a square inch is considered quite large for most medical applications. The concept of directly delivering the light from the LED directly to living tissue from the LED source itself is, therefore, contrary to laser design logic and the most likely reasoning why LEDs have never been thoroughly explored as an option for producing electromagnetic emissions for medical use.
Perhaps due to the belief that lasers are the only viable source of light applicable for use in medical treatment, or perhaps due to the belief that effective medical treatment required high energy light sources or high intensity pulsed sources (therefore leading to the widely accepted belief that lasers and similar high-intensity, monochromatic light sources are the only commercially useful sources of light), current clinical treatment regimens have been focused on applying enough energy to living tissue to heat the target molecules (i.e., water, blood, collagen, etc) therein above the minimum threshold needed to produce thermal injury. Thermal injury then occurs prior to wound healingxe2x80x94the phase in which skin begins to repair and regenerate by the formation, among many other things, new collagen fibers. For example, many laser-based treatments cause thermal injury that is believed to have a stimulatory effect by releasing chemicals which signal that the body has been wounded or injured and thus initiates a well defined sequence of events collectively termed wound healing. The end result of the wound healing mechanism may be the production of new collagen, but this occurs as a result of lethal or significant non-lethal damage to many types of cells. In contrast, through direct photoactivation (rather than a treatment regimen in which photothermal injury occurs) the direct bioactivation of a specific cell or subcellular component is triggered without appreciable levels of thermal injury or cell damage. Also, photoactivated biostimulation tends not to produce uncontrolled wound healing or abnormal wound healing (also termed scarring) as can all thermal events. Finally, there is another even higher level of thermal injury that causes protein denaturation and cell destruction and cell death. Such treatments can cause significant patient pain or discomfort and require lengthy recovery times.
Lastly, even the lowest-power lasers available for medical treatment require the supervision of qualified medical personnel. Even low-power lasers can cause at least eye damage or some degree of tissue injuries; and most lasers used for medical treatment have a risk of serious electrical shock or death. None are classified as xe2x80x98Insignificant Risk Devicesxe2x80x99, a classification for devices (such as hair dryers, electric toothbrushes, etc.) which are deemed suitable for use without medical supervision due to the minimal risks of harm or injury they pose.
It would, therefore, be desirable to have a device, and a method of using such a device, that can provide the benefits of laser treatment at significantly reduced cost and power requirement while retaining the ability to deliver sufficient intensities of narrowband, multichromatic electromagnetic radiation to living tissue to induce biostimulatory or bioinhibitory effects as part of a regimen of medical treatment. Such a treatment regimen could provide significant dermatological benefits by the photoactivation of cells to induce skin rejuvenation (i.e., the generation of new collagen) without thermally injuring the skin.
It would also be advantageous to have a source of narrowband multichromatic electromagnetic radiation and a method of using such a device to make it capable of inducing beneficial biostimulatory or bioinhibitive effect without the need to heat the tissue above the level of thermal injury, thereby essentially eliminating patient pain, discomfort, and recovery time.
It would also be a significant advancement to the art to have a device and method of using such a device that can induce beneficial bioactivating or bioinhibiting effects in living tissue that does not require medical supervision or, in at least one embodiment, pose a potential risk of eye injury, electric shock, or death.
In accordance with the present invention, the photomodulation of living tissue is achieved through the use of narrowband, mulichromatic sources of electromagnetic radiation. A preferred embodiment uses at least one light emitting diode. A plurality of these diodes may be arranged in an array to emit a wavelength from about 300 nm to about 1600 nm. Although the wavelength is chosen based on the nature of the treatment desired, preferred wavelengths include 590 nm, 644 nm, or 810 nm with a bandwith of at least +/xe2x88x925 nm.
An alternate process employs a laser diode alone or in combination with an LED or plurality of LEDs. This method may employ a continuous wave or a pulse of a period of from approximately 1.0 ms to about 1xc3x97106 ms, a light intensity of less than 1 watt/cm2, and the temperature of the living tissue not to exceed 60xc2x0 C. If further stimulation is necessary pulsing may continue from 10 seconds to 1 hour. The preferred wavelengths this process employs are 400 nm, 445 nm, 635 nm, 660 nm, 670 nm, 780 nm, 785 nm, 810 nm, 830 nm, 840 nm, 860 nm, 904 nm, 915 nm, 980 nm, 1015 nm, or 1060 nm.
Another embodiment of the method of present invention the emitter of electromagnetic radiation produces a light intensity of from about 1 nanowatt to less than about 4 watts/cm2.
Dermatological treatment may be carried out using a light emitting diode, laser diode, dye laser, flashlamp, fluorescent, filamentous, incandescent, or other emitter configured by electrical means or mechanical filtering to emit only a narrowband of wavelength centered about a dominant wavelength; and in particular 300 nm, 415 nm, 585 nm, 590 nm, 595 nm, 600 nm, 644 nm, 810 nm, 940 nm, and 1400 nm. The energy level for this process is from about 1 nanowatt/cm2 to about 4 watts/cm2 or about 200 milliwatts/cm2 to about 1000 milliwatts/cm2, wherein the exposure comprises pulsing the emitter from about 1 ms to about 1xc3x97106 ms. The pulse itself may last from about 150 ms to about 850 ms.
Further dermatological treatment suggests applying a topical agent to an area of human skin to enhance the penetration of a wavelength of light chosen for such treatment. This includes exposing the human skin to a source of narrowband, multichromatic electromagnetic radiation with a wavelength from approximately 300 nm to approximately 1600 nm for about 1 millisecond to about 30 minutes. If necessary, re-exposure every 1 to 60 days would last from 1 millisecond to about 30 minutes up to 1000 times with an interpulse interval from about 1 millisecond to about 1000 milliseconds keeping the skin temperature below the threshold at which thermal injury occurs.
Topical agents suitable for use in conjunction with the emitters of the present invention include exogenous chromophores, cosmeceuticals and, in addition, pretreatment including penetration or removal of at least some portion of the stratum corneum layer of the patient""s skin may improve treatment efficacy as will the use of an agent topically administered to adjust the absorption spectrum or refractive index of the patient""s skin. Further, topical agents applied to enhance or synergistically enhance the treatment process of the present invention may function without exhibiting the characteristics of an exogenous chromophore.
An additional embodiment for dermatological treatment is where abrasion of a segment of the skin to be treated enhances the transmission through the stratum corneum of the narrowband, multichromatic electromagnetic radiation emitter. A wavelength from about 300 nm to about 1600 nm for about 1 millisecond to about 30 minutes is used. If necessary, re-exposure may last from about 1 millisecond to about 30 minutes up to about 1000 times with an impulse interval from about 1 millisecond to about 1000 milliseconds every 1 to 60 days.